This invention relates to a thermally imagable business record, such as a form, label, tag, or the like, which may be activated to form multicolored images, and more particularly, to a substrate having a first thermally imagable coating on its surface which forms a first color when activated, and having a desensitized area and/or a masked area on at least one portion of its surface. The desensitized or masked area may be overcoated with an additional thermally imagable coating capable of forming a different color upon activation than the first thermally imagable coating.
Direct thermal printing has been a well-known means of non-impact printing. Direct thermal printers are capable of forming images by the application of heat to a substrate containing heat-reactive chemicals thereon. Typically, a substrate such as paper is coated with a thermally imagable coating of color forming and color developing reactants, which, when heated, combine and react to form a visible image. When the coated substrate passes under the print head of a thermal printer, the thermally imagable coating is activated by the heated print elements, forming images on the surface of the substrate.
Substrates coated with thermally imagable coatings provide a convenient method of printing computer generated data such as bar codes or serial numbers on business forms such as labels or tags. For example, thermally imagable substrates have been widely used as facsimile paper, bar code paper for point-of-sale (POS) systems, automatic ticket vending machines, and labels for food products. There are various compositions and methods of applying thermally imagable coatings as described, for example, in U.S. Pat. Nos. 4,865,939, 4,861,749, and 4,894,359.
However, while the use of thermally imagable coatings is a convenient method of providing a printable surface, the present method of applying the coatings is to cover the entire surface of the substrate with a thermally imagable coating which forms a single color, typically black. In certain applications, it would be desirable to be able to print multicolored images on a substrate. For example, the use of different colored images may be used to differentiate categories of information on a form.
One method for providing multiple colored areas on a business record is by applying heat at different temperatures to a coated substrate. For example, Iiyama et al, U.S. Pat. No. 4,665,410, teach a multi-color thermosensitive recording material formed by applying three or more successively overlaid thermosensitive coloring layers to a support material with intermediate layers containing a decolorizing agent. Each coloring layer yields a different color depending on the quantity of thermal energy applied. However, separate printing passes with operation at different temperatures must be made for each selected color.
Another method for providing multiple colored areas on a business record is described in commonly assigned U.S. Pat. No. 5,524,934. In this method, two or more thermally imagable coatings which produce different colors are applied by flexographic printing techniques onto selected areas of a substrate. The substrate may be activated to form different colored images by printing in a single pass. However, for some applications, it may be desirable to be able to reserve an additional print tower in the flexographic equipment to print, for example, conventional inks onto the substrate.
It would also be desirable to be able to customize different grades of thermally coated substrates by providing multicolored areas in order to accommodate different end uses. For example, thermally imagable substrates may be designed to generate bar codes which may be scanned in the infra red, visible, or near infrared ranges. Other grades may be tailored to be activated by specific printers.
Accordingly, there is still a need in the art for a business form, label or the like having thermally imagable coatings thereon which can be printed using conventional flexographic printing techniques and which may be activated in a single pass through a thermal printer to produce different colored images.